1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming apparatus capable of cutting off end portions of staples used for binding sheets, and more particularly to a sheet processing apparatus and an image forming apparatus capable of surely closing the lid which is opened when the cut-off end portions of staples are disposed of.
2. Description of the Related Art
An image forming apparatus, such as a copying machine and printer, can include a sheet processing apparatus adapted to selectively perform a stapling process or a punching process to sheets on which an image has been formed, so as to reduce work required for the stapling process or the like on image carrying sheets.
The conventional sheet processing apparatus which can perform a stapling process, can include a stapler capable of stapling a sheet bundle at one or more than one points.
In such a sheet processing apparatus, a predetermined number of image carrying sheets are transported to the process  tray, and the sheets are aligned. Then, the stapler is moved to a predetermined position at an edge of the aligned sheet bundle, and the stapler drives staples into the sheet bundle to bind the sheets.
When sheets are bound, if a small number of sheets is bound together using long-leg staples, two end portions of each staple overlap one another. To prevent the overlapping of staple legs, conventional staplers have a mechanism to cut off surplus legs. More specifically, when staples are driven through the sheet bundle, they extend to the air on the opposite side of the sheet bundle. With respect to the extending staple, only the portions of staples necessary for stapling are preserved, and after surplus portions are cut off, the remaining portions are clinched to fasten the sheets together (refer to Japanese Patent Application Laid-Open No. 2001-105347, for example).
In such a stapler, cut-off end portions H of staples are accumulated in a storage box 510 provided at a stapler 501 as shown in FIG. 20. If a stapling job is continuously performed, the storage box 510 becomes full. In this case, it is necessary to store the cut-off end portions H of staples into a large capacity storage box 600 before the storage box 510 becomes full.
When the cut-off end portions H of staples are stored in the large capacity storage box 600, the storage box 510 is moved above the large capacity storage box 600, and the open-close lid 520 provided for the movable box 510 is opened.  As the open-close lid 520 is opened, the cut-off end portions H of staples fall from the storage box 510 into the large capacity storage box 600 and collected therein.
In the conventional sheet processing apparatus and image forming apparatus, after the cut-off waste end portions H are collected in the large capacity storage box 600, the open-close lid 520 is closed, and then the stapler 501 starts a stapling operation.
However, when the staple end portions H are collected into the large capacity storage box 600, the staple end portions H sometimes can be caught in the open-close lid 520. In this case, the open-close lid 520 cannot be completely closed, and a space is made between the storage box 510 and the open-close lid 520. Under this condition, if the stapling operation is performed and the cut-off end portions H accumulate in the storage box 510, the end portions H can drop off through the space between the storage box 510 and the open-close lid 520.
Also in a stapling operation, the open-close lid 520 can open for some reason. If the open-close lid 520 opens, the staple end portions H are scattered from the storage box 510.